The functioning of randomly dumped tower packings in gas-liquid service is an art about which much has been written. For a detailed survey of this topic, presented all in one place, reference is, however, made to "Tower Packings and Packed Tower Design" (abbreviated and hereinafter referred to as TP and PTD), a book written by the inventor and published in 1953 by the United States Stoneware Company, then of Akron, Ohio.
One of the important aspects of the design and functioning of beds of randomly dumped packings involves proper design of the support plate that holds the packed bed in place in the tower. This topic has been dealt with in detail on pages 25 to 27 of TP and PTD. Suffice it, therefore, to say here that with ordinary flat support plates, in which the openings serve both liquid flow downwardly as well as gas flow upwardly, the packing pieces on top of the flat support plates tend to block the openings, with the result that the gas-liquid carrying capacity of the packed bed is thereby greatly impaired.
Having recognized this shortcoming of ordinary flat perforated supports, the author has, therefore, proposed a then novel construction embodying the "gas-injection" principle, described in TP and PTD. The principle was then implemented by simply providing flat perforated supports with a multitude of risers carrying perforations through which only the gas was admitted, separately, into the packing, a few inches above the lower terminal end of the packed bed. The liquid, on the other hand, would flow past and between the risers downwardly, and after having collected to become combined into relatively shallow liquid pools, only the liquid would discharge through the openings in the flat bottom portion of the device.
Having thus provided separate ports for gas and liquid passage, a significant improvement of the ordinary flat packing support plate had been achieved. However, since the original riser construction did not appear as economical for use in large diameter towers as was deemed necessary, the gas-injection support plates were modified by replacing the multitude of risers by longitudinal, perforated beams. This type of construction is shown in "Random Packings and Packed Towers", Design and Applications, by Ralph F. Strigle, Jr., pages 201 to 204, published in 1987 by Gulf Publishing Company.
Whereas, as already stated, the constructions embodying the gas-injection principle represent an important improvement over ordinary flat support plates, they do however still suffer from a residual drawback which is caused through the contacts which the packing pieces make with those openings that are in the flat bottom portions of gas-injection support plates. This is felt particularly in the beam type construction where the packing elements, jammed in between the beams, caused by the weight of the packing above, will block the bottom openings, causing the relatively shallow liquid pools found normally there to increase in depth. This is especially severe at elevated irrigation rates, with the result that the pool level rises and causes the liquid to discharge through openings in the beams, which were originally designed to accomodate only gas flow. It is obvious, therefore, that through this blockage of the openings by the jammed-in packing elements, the functioning of the gas-injection riser devices have been largely negated.
It has now been found surprisingly and entirely unexpectedly that the deficiencies of the gas-injection type devices just explained are completely remedied by the present invention.